Process for fabricating screens



1963 c. L. PAULLUS ETAL 3,101,526

PROCESS FOR FABRICATING SCREENS Filed Feb. 12, 1960 cw MW W 7 Q /6; 7VA? 5 W5 W rufl W. .MUB f VAN r Nfim a $0 "he 3% 4 W 3,101,526 PROCESSFOR FABRICATING SCREENS Clarence L. Paullus, Columbus, Ohio, and WillardM. Bollenbach, St. Paul, Minn, assignors, by direct and mesneassignments, 'to Edward E. Johnson, Incorporated, St. Paul, Minn, acorporation of Minnesota Filed Feb. 12, 1960,..Ser. No. 8,431

3 Claims. '(Cl. 29-1635) This invention relates to an improved processfor fabricating screens and particularly to the making of screens ofsubstantially cylindrical or flat form and of the general type describedin Johnson Patents No. 2,046,458, 2,046,- 459, 2,046,460 and 2,046,461granted July 7, 1936. "Our process is an improvement over the processfor fabricating screens described in Johnson Patent No. 2,046,461.

These patents relate particularly to well screens which must be providedina wide variety of diameters, lengths, slot widths and various sizes oflongitudinal and circumferential members. In general, m'od-ern wellscreens are of cylindrical shape and comprise a multiplicity oflongitudina'lly extending rods held in spaced parallel relation by aWrap wire the convolutions of which are joined to the several rods ateach crossing point bywelded joints. The spacing of adjacent turns ofwire determines the slot widths which must be held uniformly withinsmall tolerances for eflic'ient performance. "Geological formations fromwhich ground water supplies are obtained vary so such that everywell'tapping'these formations presents an individual problem. I This isespecially true when the water is obtained from sand and gravelformations which constitute the most" abundant and dependable sources ofwell water.

A successful screen must let sand-free water flow into the well in amplequantityand with minimumloss of head to supply the pump at'ful-lcapacity; "Thus, each screen should have slots of theproper width toprevent the passage of the sand or gravel in'a particular well. Slotsmay be required of widthsfanyWherewithin a range of .006

inch to .25 inch or more. Other elements being properly designed, thewell screen determines the capacity of the well, the draw'down'a'ndpumping head, freedom from sand, and general efficiencybf performance.

. Screen'diarneters range from approximately 1 inch to 36 inches.Adequate resistance to longitudinal forces presents no problem and'theiequ'ired range of such resistances may be readily provided byselecting longitudinal members of suitable size and suitably spacedaround the circumference of the screen} It is more difiicult, however,to provide the required wide range of resistance to lateral forcestending to collapse the cylinder. The lateral resistance to collapse isa function of the thickness, formand spacing of the circumferentialmembers.

Heretofore well screen manufacturers have at large expense maintainedlarge inventories of Wrap wire to enable them to fabricate individualscreens which meet all specifications within a wide range of wire sizesand shapes.

It is an object of our invention to provide a novel integrated processfor fabricating a screen of the class described from a substantiallycylindrical inner unit of conventional type and a thin, relatively widestrip of sheet material which is fed from a reel and given the requiredcross sectional shape by a continuous forming operation, then wrappedaround and secured to the circular array of longitudinal rods formingthe inner unit, the latter being held in conventional manner, rotatedabout its axis, and advanced longitudinally to space the convolutions ofthe wire along the inner unit.

There are circumstances in which a screen unit is used with the flow inthe direction from the inside to the outside rather than theconventional flow from the outside to 3,ll,52ti

Patented Aug. 27, 1963 2 the inside. Wire sections to meet any suchvariations in requirements may be readily formed according to thepresent invention ranging from the conventional one to a section whichprovides a slot of V-shape in cross section which widens from the innertoward the outer side.

The invention will be be'st'understood by reference to the accompanyingdrawing in which:

FIGURE 1 is a schematic illustration of apparatus for carrying out theprocess;

FIG. 2 shows successive cross sectional shapes of the wrap wire stripresulting from the first, second and third passes through the formingrolls whereby the screen is designed for flow from the outside to theinside;

FIG. 3 shows the cross sectional shape of the wrap wire produced by thesuccessive passes through the forming rolls for a screen of the typewherein flow is from the inside to the outside, and

FIG. 4 illustrates a modified form of wire which may be produced by'slight modification of the forming rolls for the third pass, a pluralityof convolutions being shown welded to a rod of the cylindrical innerunit. I

Referring to FIG. '1, a group of rods 5 constituting an inner,substantially cylindrical, unit are shown as they are held inconventional manner during the winding of a wrap wire 6 of helical formon the exterior of therods 5. .Also,.in accordance with'conventionalprocedure, the wrap wire is secured by weld joints at the several'pointsof crossing the rods 5 and current for the welding operation may besuppliedthtrough a welding roll 7 shown in contact with the wire 6 wherethe latter extends tangentially to the group of rods 5, a tangentialreach of wire being indicated at 6a.

According to our invention the wire 6 is formed continuously in timedrelation to the rotation of the rods 5 from a thin, relatively widecontinuous strip 8 of any desired. weldable material. The strip 8 is fedfrom a coil 9 supported on a bracket 10 and passes continuously to pairsof forming rolls indicated respectively by the numerals 1'1, 12 and 13;The forming rolls 11, 12 and 13 may be of conventional type, each pairhaving coacting tongue and groove or otherwise'modified peripheriesadapted to impart the required shape to the strip. Thus, as indicated inFIG. 2., the rolls 11 of the first pass may bend the marginal portions.of the strip 8 to form a channel section 14, the rolls 12. of the secondpass may produce the section indicated at 15 and the rolls 13 of thethird pass may produce a triangular finished wire section 16 which isthereupon welded to the wires 5 or other cylindrical inner unit.

Other examples of suitable formations for the strip 8 are illustrated inFIGS. 3 and 4. As shown in FIG. 4, a modification of the third passrolls 13 may be provided to form a channel shape section having spacedlongitudinally extending edges 17, both of which may be welded to therods '5 or other inner unit.

As indicated in FIG. 3, the wrap wire may be designed to permit flowfrom the inside to the outside. For such a modification the rolls offirst pass may be adapted to produce a section 18, those of the secondpass to modify this section to that indicated at 19' and the final orthird pass rolls to form the substantially U-shaped sectionshown at 20.In this case the marginal portions of the strip 8 project outwardly fromthe central portion which is welded to the rods 5 or other tubularsupporting member.

As will be evident from the foregoing, our improved process involvesessentially the feeding of a wide relatively thin strip of material froma roll of such material for forming the wrap wire, bending marginalportions of the strip to form a wire of the desired shape andcontinuously, without interrupting the feeding and forming of the wire,securing the wire to the several rods or other tubular inner unit byelectric welding, 'while rotating the inner unit about V 3 v its axisand advancing it longitudnally to space the convolutions of the wirealong the unit. The same forming operation may include the step ofbringing the sides of the wire together to provide a wrap wire ofsuitable tubular form. r

Large savings in the cost of maintaining .inventiories are effected bythe use of our process due to the tart that the strip material requiredfor the manufacture of a large range of screensmay consist of rolls ofstrip mater ial of suitable gauges. Such rolls'may be slitlongitudinally to provide strips of the width required for anyparticular screen as a part of the continuous or integrated formingprocess. Thus a single convenient width of rolled sheet material of therdesiredigau-ge may be slit longitudinally to provide any required widthwhilethe remaining sheet material may be rewound on another. roll forfuture slitting. Y

By a simple variation of strip width and adjustment of the formingrolls, both the width of the section and the depth of it may be modifiedto provide a wrap wire of any required size and shape. The slot openingfor any particular screen can be formed as a continuous helix, accordingto conventional practice, but our improved process permits fabricationof units with a given resistance to collapse for different widths of theslot openings. This will be understood when it is considered that whenfixed dimension sections of the prior art are used, the resistance tocollapse is reduced as the width of the slot opening is increased.Heretofore, it has been necessary to select from stock sizes of wire anavailable size which comes closest to providing the resistance tocollapse required for each screen According'to our process, however, thewidth and depth of the wrap wire section can be modified so that optimumproperties are obtained merely by selection of a suitable strip widthandset of form- 1 .ing rolls. for producing the required wire section.

Suitable flat strip and'sheet materials for use in construction of ourimproved well screen, are known to the art and are commonlycorrosion-resistant metals and alloys including stainless and othercorrosion-resistant steels,

bronzes and brasses. It may be desirable for some installations toprovide a tubular wrap wire with a suitable plastic core, e.g., apolyester resin or an asbestos wick or jute wick as a filler for thehollowwire. This-affords added resistance to deformation, at low cost,such a core being suitable for incorporation in the wire simultaneouslywith the forming of a screen unit. Instead of a cylindrical group ofrods 5, the inner tubular unit to receive the wrap wire may comprise aforaminous tubular unit adapted 4 a to be rotated and advancedlongitudinally during the forming and feeding of the wrap wire.

The economic advantages of our invention may be summarized as follows:(1) Reduction in the amount of metal required to produce a unit of givenspecifications, thus saving metal and reducing cost; (2) Simplicity ofstock requirements and savings in capital investment resulting from thesubstitution of a few gauges of standard flat stock at low cost perpoundfor multiple stock of special shapes and high cost per pound; (3)Reduction in the weight of the product, resulting in reduction in thecost of handling and shipping of the product, and (4) An optimumcombination of strength and costtor any required condition of service;

We claim:

1. A continuous process for making a tubular unit of the class describedwhich comprises, rotating a substantially cylindrical group oflongitudinally extending rods about its axis; simultaneously feeding athin continuous strip of material adapted to be joined by heat fusion tosaid rods; simultaneously bending longitudinally extending side portionsof said strip by a continuous operation to form an open-sided channelhaving continuous, spaced longitudinally extending side portions;continuously feeding said'channel substantially tangentially to saidgroup of rods with both of the open side edges of said side portions incontact with the rods;- and continuously, without interrupting thefeeding and bending of said strip, securing said side portions of saidchannel shaped strip at the open side thereof to the exterior surface ofsaid group of rods byelectric welding, while rotating said group of rodsas a unitabout its axis and advancing it longitudinally to spacetheconvolutions of said channel shaped member along said unit. Z

2. A process in accordance with claim 1 in which said marginal portionsof the strip are bent to extend at an acute angle one to the other.

3. A process in accordance with claim 2 in which the bending of saidstrip is continued until a tubular wire of substantially triangularshape in cross section is formed.

References Cited in the file of this patent UNITED STATES PATENTS1,266,545- Anderson May 21, 1918 1,847, 07 8 Buente Mar. 1, 19322,339,538 Zahodiakin Jan.18, 1944 2,411,988 Drieschm an et a1. Dec. 3,1946 2,473,859 Butler- June21, 1 949 2,643,863 Buscho'w June 30, 1953

1. A CONTINUOUS PROCESS FOR MAKING A TUBULAR UNIT OF THE CLASS DESCRIBEDWHICH COMPRISES, ROTATING A SUBSTANTIALLY CYLINDRICAL GROUP OFLONGITUDINALLY EXTENDING RODS ABOUT ITS AXIS; SIMULTANEOUSLY FEEDING ATHIN CONTINUOUS STRIP OF MATERIAL ADAPTED TO BE JOINED BY HEAT FUSION TOSAID RODS; SIMULTANEOUSLY BENDING LONGITUDINALLY EXTENDING SIDE PORTIONSOF SAID STRIP BY A CONTINUOUS OPERATION TO FORM AN OPEN-SIDED CHANNELHAVING CONTINUOUS, SPACED LONGITUDINALLY EXTENDING SIDE PORTIONS;CONTINUOUSLY FEEDING SAID CHANNEL SUBSTANTIALLY TANGENTIALLY TO SAIDGROUP OF RODS WITH BOTH OF THE OPEN SIDE EDGES OF SAID SIDE PORTIONS INCONTACT WITH THE RODS; AND CONTINUOUSLY, WITHOUT INTERRUPTING THEFEEDING AND BENDING OF SAID STRIP, SECURING SAID SIDE PORTIONS OF SAIDCHANNEL SHAPED STRIP AT THE OPEN SIDE THEREOF TO THE EXTERIOR SURFACE OFSAID